#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
	int a[3] = { 0 },sum=0;
	double average;
	for (int i = 0; i < 3; i++)
		scanf("%d", &a[i]);
	for (int i = 0; i < 3; i++)
		sum +=a[i];
	average = sum / 3.0;
	printf("%.3lf\n", average);
	return 0;
}